Nanoparticle-amplified surface plasmon resonance study of protein conformational change at interface

This paper reports the study of protein conformational change by Au nanoparticles (AuNPs)-amplified surface plasmon resonance (SPR) spectroscopy. Taking cytochrome c (Cyt c) as an example, this paper gives a detailed description of the construction of metal–protein–metal sandwich nanostructure consisting of an Au film underlayer, a cytochrome c intermediate layer and an AuNPs upper layer. The incorporation of AuNPs into SPR biosensing results in increased SPR sensitivity to protein conformational change as demonstrated by acid denaturation of Cyt c. It suggests the conformational change of surface-confined Cyt c leads to the distance and electromagnetic coupling variations of Au film–AuNPs. The constructed Au film–Cyt c–AuNPs sandwich is stable to repeat acid treatment using solutions in the pH range of 2.0–10.0 and yields reproducible measurements. With high sensitivity and stability, nanoparticle-amplified SPR spectroscopy can be used as a supplement method to protein conformational study. It has potential for developing novel sensors and/or switching devices in response to protein conformational change.